High voltage metal-oxide semiconductor (MOS) devices are semiconductor devices that can operate at high voltages, typically greater than about 100 volts. High voltage MOS devices find application in display drivers, power converters, motor controllers, vehicle power devices, and so on. High voltage MOS devices include laterally-diffused metal-oxide semiconductor (LDMOS) transistors and vertical-diffused metal-oxide semiconductor (VDMOS) transistors. Compared to VDMOS transistors, LDMOS transistors have faster switching speed, higher input impedance, lower power consumption, and compatibility with complementary metal-oxide-semiconductor (CMOS) processes.